One feature of the present invention involves the formation of magnesium hydroxide collodially suspended in a liquid magnesium sulfonate by reaction of magnesium oxide with a liquid hydrocarbon sulfonic acid in the presence of a portion of water relative to magnesium oxide considered by the art to be an appreciable portion of water. For example, one embodiment of the present inventive method involves the use of 11.25 weight parts of water for each 10 weight parts of magnesium oxide and such portion of water relative to alkaline earth metal oxide is indicated in U.S. Pat. No. 2,779,784 (column 2, line 29 and column 3 lines 20 to 23) as an appreciable portion of water relative to the alkaline earth metal oxide.
Said United States Patent is directed to the preparation of basic alkaline earth metal sulfonates containing an amount of alkaline earth metal in excess of the theoretical amount required to neutralize the oil-soluble hydrocarbon sulfonic acid. To accomplish this, said patent teaches that the reaction of the oil soluble sulfonic acid and alkaline earth metal oxide in the presence of the appreciable portion of water must be carried out under superatmospheric pressure (2 to 10 atmosphere at column 3, lines 29-30) to maintain the water in the liquid phase at temperatures above 104.4.degree. C. This combination of pressure and reaction temperature above 104.4.degree. C. is said to be required to form a stable dispersion of the excess alkaline earth metal reactant.
The excess amount of alkaline earth metal reactant related to the stoichiometric requirement to exactly neutralize the sulfonic acid contemplated in U.S. Pat. No. 2,779,784 (column 3, lines 11 to 16) is from 110 up to 220 percent but from a practical standpoint use of an excess of more than 200 percent results in unreacted alkaline earth metal oxide which is removed by an essential filtration step. The alkaline earth metal sulfonate products produced by the elevated temperature and superatmospheric pressure method of said patent conducted for two hours had a total base number of 30.9 and 4.8 which were more than double the total base number of products resulting from the same products not produced under superatmospheric pressure.
We have, however, discovered an improved method for preparing a 400 and higher total base number magnesium sulfonate product in a relatively short reaction time to provide a relatively low viscosity, stable suspension of the excess magnesium reactant.